Farms across the globe have been adding sugar to the diet of dairy cows for either altering the composition of milk to favour protein or the assumed benefit of increased milk production. In this article, we have broken down the composition of a cow’s diet and the effect of adding/replacing sugar. Well, for one thing, My cow has a sweet tooth. Let’s see, would adding sugar increase milk production or not!
Many farms across the globe add sugar to the pasture-based dairy cow’s feed. This is a classic ingredient with ruminant nutrition.
It is a fact that adding sugar alters milk composition. It is a common notion that adding sugar increases milk production.
To prove or disprove this argument, let’s explore what sugars are, how they are broken down in cow’s rumen and what effect they would have on lactating cows. It is true that feeding sugar increases the (protein/fat content of the milk) and brings in more capital. But the big question is, would added sugar increase milk production?
Composition of Dairy Cow Diet
A cow needs a daily intake of nutrients. These are carbohydrates, fats, proteins, amino acids, vitamins, and minerals. Carbohydrates make up the biggest chunk of a cow’s diet, comprising approximately 70% of the entire feed intake. Carbohydrates are the main source of energy for rumen microorganisms and milk production.
Altering the composition of carbs in a dairy cows’ diet changes the percentage of fat, protein, and lactose in the milk. This altered composition has the potential to fetch more capital, thus there is a great incentive for the farm management to control the carbohydrate composition and intake.
What are carbohydrates
Carbs are comprised of sugar, starches, and fibres. Since forages, grains, and pasture are the biggest source of the dairy cow diet we will pay more attention to plant carbohydrates.
Carbohydrates are compounds of carbon, hydrogen, and oxygen (CHO). Carbs can be divided into two groups.
1. Structural Carbohydrates
Structural carbohydrates make up the plant cell walls. Pectins, lignins, hemicellulose, and cellulose are the main content of cell walls. Fibrous content maintains the pH of the rumen thus boosting the rumen health.
2. Non-structural Carbohydrates
They make up the inner content of cells and are easily digestible as compared to structural carbohydrates. The inner content of cells is the organic acids, sugars, starches, and fructans. They are also called simple carbohydrates as they are readily fermented.
Carbs are broken down in cow’s rumen
There are good microbes in cow’s rumen. These microbes ferment all the carbs. However, the soluble non-structural carbs are fermented quickly and readily provide energy as compared to the structural carbs.
Cell wall material takes a lot of time to ferment. As the plant matures, lignin is formed in their cell walls and thence makes it difficult to break the bonds and ferment. But once fermented, plant material proves to be a good source of energy for lactating cows.
Bonus Point: If there is enough pasture available for the dairy cow, then pasture is enough.
There is a positive relationship between milk fat content and ruminal pH. If ruminal pH is low, the fat content in the milk is reduced as a result. In the early lactation period, high producing cows are more sensitive to rumen acidosis.
However, their milk fat content is less sensitive to ruminal pH. Farm management ought to take careful measures and ensure early lactating cows are not deprived of energy and do not mobilize body fat. In case dairy cows mobilize body fat, the fat content in the milk will increase.
Keep in Mind: The milk fat-to-protein ratio can be used as an indicator of underlying problems like energy deficiency, ruminal pH, and subclinical ketosis.
Would replacing Pasture with high sugary feed increase milk production?
Well, it’s trendy to add sugar to the dairy cow diet. Like I stated earlier, sugars are simple carbohydrates and ferment easily, readily providing energy to the dairy cow. (Who said that my cow had a sweet tooth? :-D)
Theoretically, 35-40% soluble sugars and stretches in dairy cows maximize milk production. On the other hand, spring pasture contains less soluble sugars and starches than that.
However, in the good quality leafy pasture, the structural carbohydrates are highly digestible, 70 to 80%. Thus, structural carbohydrates may take a bit longer to ferment and break down but they provide similar energy as soluble sugars would.
It’s all thanks to microbes in cow’s rumen for breaking apart the bonds in structural carbs so the sugar in them can be used to provide energy.
Conclusion: It takes an increased total amount of energy in the diet for the rumen bugs to generate more energy and as a result increase milk production. Replacing pasture with a feed that is high in sugar or starch will not generate more energy.
Effect of added sugar on Dairy Cow Productivity
It is proven in literature and research that adding sugar to the diet of lactating cows increases their intake of dry matter. The best practice when adding dietary sugar is to keep it 2.5-5% of DM. An amount greater than this may reduce milk yield.
The addition of sugar depends on the sugar content of the diet. Fresh forage and hay have higher concentrations of sugar as compared to corn silage. Similarly, the sugar content of the feed also depends on the time of the day as pasture has the highest sugar content in afternoons.
For best results, the adequate value of forage at NDF (structural carbohydrates) of 19-21%, starch at 25%, non-fibre carbs (included sugars) at less than 40% must be provided.
Fun Fact: Dairy cows are said to recognize the sweet taste. So if you offer up choices, your cow will prefer eating the sweetest food. No wonder my cow has a sweet tooth :-D
Would adding sugar change Milk Composition?
Yes, it’s true that changing the composition of dairy cows’ diet will alter the composition of the milk. The addition of sugar and starch to the diet of grazing cows will increase protein content in the milk and decrease the fat content.
Let me state this again, adding sugar will not increase the energy generated in the rumen nor the milk production. To increase milk productivity total energy of the diet has to be increased for the rumen bugs to generate more energy.
This brings us to the end of this article- until we meet again, Happy Grazing!
- The Dedicated Team of Pasture.io, 14 March 2022